Directional audio propagation technology refers to a technology to propagate sound in a directional manner so that only human ears in a predetermined zone can hear the sound. The directional audio propagation technology has a very wide range of application scenes, for example, when a user is watching TV, the TV set can send sound into a predetermined zone by the directional audio propagation technology, and as a result, the user can hear the sound of a TV program once he/she enters the predetermined zone, but the user cannot hear the sound once he/she walks out of the predetermined zone.
However, the directional audio propagation technology in prior art typically can only transmit all the audio signals emitted by a terminal device into the predetermined zone, without discriminating the audio contents, which is an inflexible way of audio propagation. In some special scenes, multiple users in different locations may have mutually different demands for audio contents, for example, the “one screen two displays” function of a TV set is a function that allows one screen to simultaneously play two kinds of images, a TV set with such a function is also called double-channel TV set. Irrespective of whether it is called “one screen two displays” or double-channel TV set, both actually utilize the principle of 3D TV image display, a group of 3D TV manufacturers represented by Kanka call it “double-channel”, while another group of 3D TV manufacturers represented by TCL call it “one screen two displays”. On the German IFA exhibition of the year 2012, this type of product is exhibited by Samsung, LG and TCL, and attracts interest from many German citizens. In the “one screen two displays” mode or double-channel mode of a TV set, if the user wears no glasses when watching the TV images, there would be a phenomenon of double imaging, this is because two different signal sources are being received and displayed by the TV set. For example, a double-channel TV set can on one hand play a Blu-ray movie and on the other hand display a car racing game of PlayStation 3 at the same time, and two users only need to put on all-left 3D glasses or all-right 3D glasses respectively in order to watch their respective images without mutual influence. Under such circumstances, users wearing different glasses watch different TV programs, but different TV programs correspond to different audio contents (e.g. different audio language types and different audio contents), therefore, the users also need to wear special earphones in order to hear corresponding audio content, otherwise there would be audio interference. However, wearing an earphone not only has a high cost, but also adversely affects the audiovisual experience of the users.
Therefore, how to improve the versatility of directional audio propagation and enhance the audiovisual experience for users is a technical problem that urgently needs to be solved.